Ms Bishop was present during the call, in the same room as Mr Turnbull, but didn't speak, the sources said.

From the conversation, it was clear that Mr Turnbull wanted her to be his deputy. "We basically agreed - Turnbull as leader, Bishop as deputy and Morrison as treasurer," is how one participant summarised the conversation to a colleague.

It was precisely this arrangement that became reality when Mr Abbott lost the leadership to Mr Turnbull in September.

Mr Morrison was the social services minister at the time and Mr Turnbull communications minister. Ms Bishop was already deputy leader.

Malcolm Turnbull and Julie Bishop arrive at Rosemont House in Woollahra for Liberal Party fundraiser in February.

Photo: Edwina Pickles

Like Mr Morrison, she was wary of committing to any firm arrangement.

She wanted to keep open the option of running for the leader's position herself.

Prime Minister Malcolm Turnbull and Treasurer Scott Morrison.

Photo: Andrew Meares

Although the discussions were deliberately inconclusive, they nonetheless formed the basis for an understanding that remained tacitly in place as the trio continued to serve in the Abbott cabinet for the next seven months and six days.

There was speculation at the time that the three might come together to form a team or "ticket", but until now there has been no knowledge that they had canvassed such a contingency.

Mr Turnbull was quietly weighing the option of challenging Mr Abbott the next day and wanted to have his leadership team in place, but in the event decided that there was not enough support.

The call took place when Mr Turnbull and Ms Bishop happened to be at the same fundraising event in a private home in the Sydney suburb of Woollahra on Sunday, February 8. They repaired to a quiet room and closed the door for privacy.

Mr Turnbull phoned Mr Morrison, who was in his car driving to Canberra for the spill the next day. The phones at both ends of the call were switched to speaker-phone.

"Shirtfronted" also discloses that Barnaby Joyce has blamed the relationship between Mr Abbott and his then chief of staff, Peta Credlin, for giving Ms Credlin too much power.

Mr Joyce, the Agriculture Minister in the Abbott and Turnbull governments, said that, when ministers wanted approval for a proposal, "it was a two-hurdle race - you had to get Tony Abbott and Peta Credlin and line them both up.

"It creates real difficulty for a politician when they have to lobby someone who's not elected," said Mr Joyce. "There was too much control from Tony's office."

The series also reports that Mr Abbott's most loyal supporters, including his numbers man Eric Abetz, explicitly told him after the February spill that he needed to dump Ms Credlin and his treasurer, Joe Hockey, if he hoped to keep the prime ministership.

Peter Hartcher is the political editor and international editor of The Sydney Morning Herald. He is a Gold Walkley award winner, a former foreign correspondent in Tokyo and Washington, and a visiting fellow at the Lowy Institute for International Policy.